1. Field of the Invention
This invention relates to position sensors, and more particularly to a position sensor with a resistive strip and a termination clip for connecting the resistive strip to an electrical terminal.
2. Description of the Related Art
Prior art throttle position sensors, such as disclosed in U.S. Pat. Nos. 5,321,980 and 5,133,321 to Hering et al. and U.S. Pat. Nos. 5,416,295 and 5,385,068 to White et al., the disclosures of which are hereby incorporated by reference, typically include an external housing with a sensor substrate and rotor positioned in the housing.
FIG. 1 is an assembly view of a prior art throttle position sensor 16 exploded along line 34. The sensor 16 comprises an external housing 50, a seal 52, a screened film substrate or sensor element 54, a termination wedge 56, a rotor 58, a spring 60, and a cover 62. Terminals (not shown) extend from within a connector portion 48 to the interior of the housing 50. The terminals within the housing 50 are supported by a web 64. An electrical cable with a corresponding number of conductors (not shown) interconnects with the terminals at the connector portion to thereby electrically connect the terminals to an electronic fuel control system (not shown). The screened film substrate 54 includes a resistive element 66, an idle conductive element 68, and a throttle conductive element 70 that are etched onto the substrate 54. A nonconductive portion 69 separates the idle and throttle conductive elements. A rotor 58 includes a throttle wiper 72 and an idle/throttle validation wiper 74.
In assembly of the sensor 16, the seal 52 is first inserted within the housing 50. The substrate 54 is then positioned in the housing such that a flat portion 76 of the substrate rests adjacent the web 64 with the elements 66, 68 and 70 facing inward. The substrate 54 includes additional electrical traces (not shown) for coupling the elements 66, 68 and 70 to suitable terminal contact points (not shown) on the flat portion 76. The termination wedge 56 is then inserted between the flat portion 76 of the substrate 54 and a wall 65 of the housing 50 to thereby press the substrate against the web 64 and interconnect the elements 66, 68 and 70 of substrate 54 to the terminals supported by the web 64. Electrical coupling between individual conductors of the cable and portions of the substrate 54 is thereby established by the wedge 56. The rotor 58 is then installed in the housing 50 such that the wiper 72 contacts element 66 and wiper 74 contacts a first portion 69 or one of the elements 68 or 70. The spring 60 is then coupled between the rotor 58 and housing 50 to bias the rotor toward a full return position. The cover 62 is finally attached to the housing 50 to rotatably support the rotor 58 and to seal the entire assembly.
The termination wedge 56 in the above-described arrangement applies a force against the web 64 and causes it to deflect. Microcracks and/or stress hardening in the web may occur and lead to early failure of the sensor, especially when subject to vibration, as is common in automotive applications. The termination wedge 56 is also difficult to install since the flat portion 76 of the substrate 54 is initially unrestrained when inserted into the housing 50. Moreover, the relatively high contact point of the wedge 56 on the flat portion 76 leaves little room for routing traces on the substrate.
Other prior art position sensors using sensor substrates include U.S. Pat. No. 5,460,035, U.S. Pat. No. 5,415,144, U.S. Pat. No. 5,039,975, U.S. Pat. No. 4,703,649, U.S. Pat. No. 4,688,420, U.S. Pat. No. 4,616,504, U.S. Pat. No. 4,435,691, U.S. Pat. No. 4,430,634, U.S. Pat. No. 4,334,352, and U.S. Pat. No. 3,643,198, the disclosures of which are hereby incorporated by reference.